Open air stove

ABSTRACT

An open air stove comprises a fuel supply line which can be connected to a fuel source, a fuel nozzle which is connected to one end of said supply line and which extends into a cylindrical inner part of an inner cup. The inner cup is mounted concentrically in a partially cylindrical outer cup, so that the cylindrical part of the inner cup extends at least partially into the cylindrical part of the outer cup. The relationship between the nozzle hole diameter φ m , the inner diameter φ of the cylindrical part of the inner cup, and the inner diameter φ y  of the cylindrical part of the outer cup is such that when φ m  lies in the range of 0.28-0.37 mm φ i  will have the value  24  +/−5 mm and φ y  will have the value  60  +5/−10 mm.

FIELD OF INVENTION

The present invention relates to open air stoves that use connectablefuel sources.

BACKGROUND OF THE INVENTION

These open air stoves either use gaseous fuels such as bottled gas forinstance, which is a mixture of propane and butane, or some other typeof liquid fuel, such as paraffin, ethanol, diesel, methanol or gasoline.Stoves that use bottled gas must be of an approved type, and must fulfilcertain requirements with respect to temperature values and emissionvalues in order to be approved. Stoves that have been constructed forliquid fuels do not have to meet corresponding requirements, and henceconstruction of such stoves has been directed solely towards eithergas-fired stoves or solely towards stoves that are fired with liquidfuels. A stove that has been constructed for bottled gas is not suitablefor use with paraffin, since the stove has been constructed with astarting point from a liquid fuel source. The type of fuel source forwhich the stove is constructed controls geometries with respect tovaporisation loop, fuel pipe diameters, nozzle design, the diameter ofthe nozzle orifice, air holes, etc.

It might be possible to use a stove designed for gaseous fuels with theaforesaid liquid fuels as a fuel source, provided that certainmodifications were made with respect to coupling of of the fuel sources,although this would result in a very large difference between the powergenerated by the stove when using liquid fuel that has a high airrequirement (paraffin, diesel) and when using bottled gas, and the stovewould be very difficult to ignite. Consequently, a modified constructionof this kind is completely uninteresting to the user. From a useraspect, a stove that is operated on gaseous or liquid fuels willpreferably be able to heat 1 liter of water to a temperature of 20° C.in a maximum of 3-4 minutes, regardless of the type of fuel used. Thestove shall also be compact, so as to enable it to be tucked away in asmall space, and will also achieve complete combustion as far aspossible, so as to avoid sooting.

OBJECTS OF THE INVENTION

One object of the invention is to provide a stove that can be usedeither with gaseous fuels, such as bottled gas, or with paraffin,diesel, alcohol or gasoline . Another object is to provide such a stovethat also fulfils the requirements laid down with respect to officialapproval of the type of stove concerned, and user requirements withrespect to efficiency, flexibility, function, size and cleanliness.

SUMMARY OF THE INVENTION

In order to provide a stove which satisfies these objects, there isrequired a special combination of geometries in a special design of thestove, which means in the present case a unique combination of diameterson a cylindrical inner cup and diameters on a cylindrical outer cup, incombination with the diameter of the burner nozzle orifice. Thesegeometries and special means for connecting different fuel sourcesconstitute the present invention as defined in the following Claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described in more detail withreference to the accompanying drawings, in which reference signs havebeen included.

FIG. 1 is a sectional view of a stove according to the presentinvention.

FIG. 2 is a sectional view of part of the connection of the burnernozzle shown in FIG. 1.

FIG. 3 is a sectional view of a regulating valve according to oneembodiment of the invention.

FIG. 4 illustrates an adapter for use in conjunction with the presentinvention.

DESCRIPTION OF THE INVENTION

FIG. 1 shows an open air stove 1 that includes a fuel supply line 2whose one end is connected to a burner nozzle 3. The burner nozzle 3 ismounted at the bottom of an inner cup 4 that includes a lowercylindrical inner part 5 having an internal diameter φ_(i) and an upperfunnel-shaped inner part 6. The burner nozzle and the end of the fuelsupply line are mounted in a bottom piece 7 that extends into the innercup 4 from beneath. The bottom piece also constitutes a spacer betweenthe inner cup and an outer cup 8 mounted concentrically around saidinner cup. The nozzle-carrying end of the fuel supply line 2 is providedwith a vaopourization loop F whose upper part has a circle-sector shape.

The outer cup 8 also includes a lower cylindrical outer part 9 having aninner diameter φ_(y) and an upper funnel-shaped outer part 10. Thecylindrical part of the inner cup has extending around its periphery aplurality of primary-air holes 11 through which combustion air issupplied. The cylindrical part of the outer cup is provided with airholes 12 through which primary air is supplied to the burner, secondaryair is supplied to the flame, and combustion air is supplied in apre-heating process.

The illustrated stove also includes at least three legs 13 which aremounted for pivotal movement about a respective pivot pin 14 arrangedparallel with the cylindrical axis 15 of the inner cup at the bottom 16of the outer cup. Each leg 13 has a vessel support means 17 attachedpermanently thereto. Thus, each leg and its associated vessel supportmeans can be rotated about its pivot axis towards one side of the stove,so as to minimise the volume of the stove.

FIG. 2 illustrates a part of the rotational-symmetrical bottom piece 7with the pressed-fitted end 18 of the fuel supply line 2 extendingradially outwards from the bottom piece 7 beneath the bottom 19 of theinner cup 4. The bottom piece 7 includes a cylindrical neck 20 whichextends in through the bottom 19 of the inner cup 4 and which is fittedconcentrically in said inner cup. The burner nozzle 3 has a thread 21and an hexagonal head 22, which enable the nozzle to be screwed down inthe neck 20 of said bottom piece. The nozzle also includes a fuel hole23 in its upper part. The hole diameter φ_(m) of the nozzle lies in therange of 0.28-0.37 mn.

Certain geometries are of decisive significance in providing a stovethat has the properties mentioned in the introduction. These geometriesare

1. The nozzle hole-diameter φ_(m);

2. The inner diameter φ_(i) of the cylindrical part of the inner cup;and

3. The inner diameter φ_(y) of the cylindrical part of the outer cup.

The relationship between the diameter φ_(m) of the fuel-hole 23 in thenozzle, the inner diameter φ_(i) of the cylindrical part 5 of the innercup 4, and the inner diameter φ_(y) of the cylindrical part of the outercup is such that when φ_(m) lies in the range of 0.28-0.37 mm, φ_(i)will have the value 24 +/−5 mm and φ_(y) will have the value 60 +5/−10mm. The diameter measurements given above are optimum values. However,the values may deviate from the given optimum values to some extentwithout having a too deleterious effect on functional requirements. Therange 0.28-0.37 mm means that the stove can be manufactured in differentsizes for different powers, while still fulfilling the functionalrequirements. Different combinations between these three sets of valuesare conceivable, depending on which fuel is chosen as the primary fueland which fuels are chosen as the secondary fuels. Since different fuelshave different burning properties, a particular fuel is always chosen asthe primary fuel from the aspect of construction.

The following designs are advantageous with respect to said geometrieswhen φ_(m) lies in the range of 0.28-0.37 mm.

1. φ_(i) has the value 19-29 mm and φ_(y) has the value 50-65 mm

2. φ_(i) has the value 21-27 mm and φ_(y) has the value 53-64 mm

3. φ_(i) has the value 22-26 mm and φ_(y) has the value 55-63 mm

4. φ_(i) has the value 23-25 mm and φ_(y) has the value 58-62 mm

5. φ_(i) has the value 24 mm and φ_(y) has the value 60 mm

The diameter φ_(i)=24 mm and φ_(y)=60 mm are optimum values with respectto power in relation to compactness. The diameter φ_(i) together withstove power determines the size of the primary-air holes 11.

The main functions of the outer and inner cups 8, 4 are directly relatedto the aforesaid geometries. The outer cup acts as a windshield; as anevaporation fuel storage means at the start; and as a radiation shieldwhich retains heat for the vaporization loop on the one hand and, on theother hand, reduces radiation outside the cup; and as means for holdingsaid legs and said nozzle, and to concentrate the flames around thevaporising tube when starting-up the stove. The inner cup functions as aflame holder, and as a means for mixing air and fuel (possiblyvaporised), and to conduct heat to the attachment thereof so as toenhance the vaporisation. These functions are highly dependent on thedimensions of the outer cup 8 and the inner cup 4, in order to achieveoptimum functioning of the stove and optimum combustion of the fuel.

The other end of the fuel line is connectable to a fuel source (notshown) via a regulating valve 24 (see FIG. 3) which controls the burningpower of the stove by opening and throttling the fuel flow respectively.The regulating valve 24 includes a knob 25 attached to a valve spindle26 which is sealed against a valve housing 27 by means of an O-ring 28.The fuel line 2 is connected to the valve housing 27 via a coupling 29,which may either be separable or fixed. In this regard, the fuel line 2may be divided into a metal part proximal to the stove and be connected,via a coupling, to a flexible hose system for connection to theregulating valve. The valve housing also includes a fuel sourceconnection 30, said connection including a seal 31 and an opening pin32.

When the stove 1 is to be connected to a gas bottle, the regulatingvalve 24 is screwed directly onto the bottle and the opening pin 32functions to open a check valve in the bottle in a conventional manner.

When the stove 1 is to be connected to a conventional pump system forliquid fuel, the regulating valve 24 is screwed firmly to an adapter 33(FIG. 4) which is designed for connection to the pump system, wherewiththe opening pin 32 opens a check valve 34 in the adapter so that thepressurised fuel in the pump system will reach the valve and the flow offuel to the stove regulated by said valve. The adapter is firmlyconnected to the pump system and functions to enable the system to becoupled to different fuel systems without needing to change theregulating valve and the hose system. When switching from a liquid fuelto a gaseous fuel, the regulating valve is unscrewed from the adapter33, wherewith the check valve 34 closes and therewith prevents thepressurised liquid from flowing out from its container. The regulatingvalve is then screwed onto, e.g., a standard-type gas bottle. The stovecan then be used as a gas stove, by opening the spindle 26 of theregulating valve 24. correspondingly, the check valve on the gas bottleis closed when the valve is unscrewed from the bottle.

I claim:
 1. An open air stove which comprises a fuel supply line, oneend of which can be connected to a fuel source and the other end ofwhich includes a vaporisation loop, and which further comprises, at saidother end of the fuel supply line, a burner nozzle, which has a nozzlehole defining a nozzle hole diameter φ_(m) and which extends into acylindrical part of an inner cups said inner cup being mountedconcentrically in a cylindrical part of an outer cup such that thecylindrical part of said inner cup extends at least partially into thecylindrical part of said outer cup, wherein the cylindrical part of theinner cup defines an inner diameter φ_(i) and the cylindrical part ofthe outer cup defines an inner diameter φ_(y) and wherein the stove isadapted for selective use either with gaseous fuel or with liquid fuelby virtue of the relationship among the nozzle hole diameter φ_(m), theinner diameter φ_(i) of the cylindrical part of said inner cup, and theinner diameter φ_(y) of the cylindrical part of said outer cup beingsuch that φ_(m) lies in the range of 0.28-0.37 mm, φ_(i) has the value24 +/−5 mm, and φ_(y) has the value 60 +5/−10 mm.
 2. A stove accordingto claim 1, wherein each of the inner and outer cups has a symmetry axisand wherein the burner nozzle is cylindrical and has a symmetry axis,which is parallel with the symmetry axis of the inner cup and with thesymmetry axis of the outer cup.
 3. A stove according to claim 1, whereinthe burner nozzle hole faces in the direction of the symmetry axis ofthe burner nozzle.
 4. A stove according to any one of claims 1-3,wherein a major part of the vaporisation loop is placed in a spacebetween the outer cup and the inner cup.
 5. A stove according to any oneof claims 1-3, wherein the fuel supply line at the end that can beconnected to the fuel source, carries a regulating valve for regulatingthe amount of fuel supplied to the stove.
 6. A stove according to claim5, wherein the regulating valve can be connected to an adapter, whichincludes a check valve and which is firmly connected to a liquid fuelpump system.
 7. A stove according to claim 5, wherein the regulatingvalve can be connected to a gas-bottle fuel source.
 8. A stove accordingto any one of claims 1-3, wherein the outer cup has a bottom, wherein atleast three legs are pivotally mounted on the bottom of the outer cup onrespective pivot pins, and wherein each of said legs has a vesselsupport means firmly connected thereto.
 9. A stove according to claim 8,wherein at least two of said legs can be swung around the periphery ofthe outer cup to one side thereof, so as to minimise the volume of thestove.
 10. A stove according to any one of claims 1-3, wherein the innercup and the outer cup widen into a funnel-shaped inner part and afunnel-shaped outer part respectively at their upper ends.